DENVER — The ad seems like an artifact from an earlier political era — a grainy mug shot of a convicted murderer, flashing police lights, a recording of a panicked 911 call and then a question about Colorado's Democratic governor, up for re-election next year: "How can we protect our families when Gov. Hickenlooper allows a cold-blooded killer to escape justice?"

The online spot from the Colorado Republican Party appeared only hours after Gov. John Hickenlooper in May indefinitely suspended the death sentence of Nathan Dunlap, who killed four people in 1993 and was scheduled to be executed in August. The governor cited problems with the concept and application of the death penalty.

Eclipsed by economic issues and other social concerns, crime is slowly re-emerging as a campaign issue.

From the 1960s to the early 1990s, Republicans hammered Democrats on crime for focusing too much on rehabilitation and not enough on punishment and imprisonment. That changed as crime rates plunged in the 1990s and Arkansas Gov. Bill Clinton inoculated Democrats by being an avid death penalty supporter, interrupting his 1992 presidential campaign to preside over an execution.

Now increasing numbers of states are turning away from mandatory prison sentences and embracing rehabilitation programs to thin out inmate populations and save taxpayer money. The shift has been particularly pronounced in conservative, Republican-dominated states like Georgia, Texas and South Carolina.

That growing consensus is facing its first test in two political bellwether states where demographics have pushed Republicans into a political corner.

In Colorado, Republican Rep. Mike Coffman held his seat last year partly by attacking his challenger for failing to support a proposed state law to take DNA samples from people arrested on suspicion of committing felonies, and the GOP is hoping crime issues will help them unseat Hickenlooper and win back control of the state legislature in 2014. They have attacked Democrats for rejecting legislation to impose mandatory sentences of 25 years to life on sex offenders, and for passing a law limiting prosecutors' ability to charge juveniles as adults. GOP leaders are trying to persuade the district attorney whose office prosecuted Dunlap to run for governor.

Republicans say they have no shortage of issues to run on in Colorado. But one, they say, stands out for its potency.

"Crime, justice, law and order, public safety resonate in a more personal way than a chart and graph of GDP growth," said Ryan Call, chairman of the Colorado Republican Party.

In California, which has conducted the most ambitious criminal justice overhaul in the nation, Republicans are targeting Gov. Jerry Brown and legislative Democrats over the state's policy that sends lower-level offenders to local jails rather than state prisons. The law went into full effect in late 2011, but already there have been several highly publicized cases of convicts released from prison committing crimes like rape and murder. The most prominent Republican to emerge as a possible challenger to Brown, former Lt. Gov. Abel Maldonado, in May launched a ballot campaign to reverse the prison overhaul.

Frank Zimring, a University of California-Berkeley law professor who has written widely on crime and politics, noted that crime rates appear to have leveled out after a two-decade decline. He called the recent GOP efforts "the test run as to whether there could be a resurgence in hard-right, punitive" crime politics.

In California, the Republican Party has no statewide office-holders and less than one-third of the seats in the state legislature. In those circumstances, Zimring said, "you consult your greatest hits playbook from previous eras."

It's unclear if those attacks will resonate in an era that still features historically low crime rates and one in which voters have shown a willingness to reconsider tough crime laws. In California, for example, a ballot measure to roll back part of the state's controversial 1994 three-strikes law — it requires 25 years to life in prison for people convicted of a third felony — passed with 70 percent support in November.

"There certainly are signs that politicians are trying to use it as a wedge issue," said Marc Levin of Right on Crime, a Texas-based group that pushes flexible sentences and rehabilitation programs from a conservative perspective. "But I'm struggling to see a legislator who got voted out of office in the last several years for supporting criminal justice reform."

The change in crime policy dates back to 2007, when Texas legislators balked at building three new prisons. They instead passed laws giving judges greater flexibility to send offenders to local facilities or probation. As tax revenues cratered during the recession, other states scrambled to cut incarceration costs.

"It used to be 'how do we demonstrate that we're tough on crime?'" said Adam Gelb, director of the Public Safety Performance Project at the Pew Charitable Trusts. "Now it's 'how do we get taxpayers better returns on their criminal justice dollars?'"

In California, legislative Republicans opposed Brown's prisons plan, but that did not matter because Democrats have such overwhelming numbers in the statehouse. The plan was the governor's response to a federal court order that required the state to reduce its overcrowded prison population. Since Brown's plan became law the population has dropped nearly 10 percent, but federal judges last month ordered the release of 9,600 more inmates to comply with previous rulings. Brown has refused to release more prisoners and said that he will take the case to the U.S. Supreme Court first. His office declined to comment for this story.

Amid that backdrop, several crimes have been blamed on the early releases.

Michael Rushford, president of the Criminal Justice Legal Foundation in Sacramento, said the controversy reminds him of California's perennial back-and-forth on crime. In the 1960s, state prison populations began to shrink, with the greatest reduction coming during the first term of Gov. Ronald Reagan. But by the end of that decade the numbers were on the rise again.

"We've seen this before," said Rushford. "The policy swings one way and it goes too far. People get unhappy about it, it swings another way. Now people feel guilty, it swings again."

Rushford's group released a study this month that found preliminary FBI crime statistics indicate an abrupt rise in crime in California last year. But skeptics say the early numbers are not reliable and more time is needed to get a sense of the impact of the prison shift.

Politically, Democrats are preparing for a fight. They have not had to worry much in recent years, as the state has become a stronghold for their party.